Optical system and image displaying apparatus using the same

Abstract

The present invention has as its object to provide an optical system which can generally be easily made compact and light in weight and wide in angle of field when image information displayed on a display unit such as a liquid crystal display is observed, and an image displaying apparatus using the same. To achieve this object, the optical system according to the present invention is an optical system for directing a beam from the display unit to a predetermined position to thereby enable an observer to observe image information on the display unit, and when a ray emerging from the center of the display surface of the display unit and passing through the center of the exit pupil of the optical system is defined as a central field angle principal ray, the optical system has a first optical element having on the same member a plurality of eccentric reflecting surfaces eccentric relative to the central field angle principal ray and having power, and an eccentric mirror system comprising at least one eccentric mirror eccentric relative to the central field angle principal ray and having power, and directs the beam from the display unit to the first optical element through the intermediary of the eccentric mirror system and directs the beam emerging from the first optical element to the predetermined position.

1. An optical system for directing a beam from display means to a predetermined position, wherein a ray emerging from the center of the display surface of said display means and passing through the center of the exit pupil of said optical system is defined as a central field angle principal ray, said optical system comprising:
 a first optical element having a plurality of eccentric reflecting surfaces, each of the eccentric reflecting surfaces having power and being eccentric relative to the central field angle principal ray, and  
 an eccentric mirror system comprising at least one eccentric mirror having positive power and eccentric relative to the central field angle principal ray,  
 wherein the beam from said display means is condensed and directed to said first optical element by said eccentric mirror system; and  
 wherein said optical system has refractive power capable of forming an intermediate image in an optical path leading from the display means to the predetermined position;  
 wherein the central field angle principal ray does not intersect on the optical path in said eccentric mirror system; and  
 further comprising at least two surfaces, each of which has power, respectively disposed in the optical path before the intermediate image is formed and between the intermediate image and the exit pupil of said optical system.  
 
   
   
     2. An optical system according to  claim 1 , wherein said first optical element has a reflecting and transmitting surface having power serving as an eccentric reflecting surface and a transmitting surface. 
   
   
     3. An optical system according to  claim 2 , wherein said reflecting and transmitting surface has a common area on which both of a reflected beam and a transmitted beam impinge, and the reflection on at least said common area is the internal total reflection in said first optical element. 
   
   
     4. An optical system according to  claim 3 , wherein a reflecting film is formed on a portion of said reflecting and transmitting surface. 
   
   
     5. An optical system according to  claim 1 , wherein the intermediate image is formed larger than an image displayed on said display means. 
   
   
     6. An optical system according to  claim 1 , wherein at least a portion of said intermediate image is formed in the first optical element. 
   
   
     7. An optical system according to  claim 1 , wherein the display surface of said display means is a flat surface, and said intermediate image is curvedly formed. 
   
   
     8. An optical system according to  claim 1 , wherein at least one of said eccentric reflecting surfaces is of a non-rotation-symmetrical shape having only one symmetrical plane. 
   
   
     9. An optical system according to  claim 1 , wherein a beam passing through said first optical element is reflected three or less times. 
   
   
     10. An image display apparatus comprising:
 an optical system according to  claim 1 ; and  
 displays means for displaying image information.  
 
   
   
     11. A head mount display comprising:
 an image display apparatus according to  claim 10 ; and  
 a head mount mechanism.  
 
   
   
     12. An optical system according to  claim 1 , wherein when in a plane formed by said central field angle principal ray, the angle formed when rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil emerge from said display means and are incident of a first mirror of said eccentric mirror system is defined as θin, and the angle formed when the rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil emerge from the last eccentric mirror of said eccentric mirror system is defined as θout, and the angle formed when the point of intersection is formed on the reflected side when the rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil are extended is defined as positive, and the angle formed when the point of intersection is formed on the opposite side is defined as negative, said eccentric mirror system is designed so as to satisfy
   0≦θout/θin≦1.  
 
   
   
     13. An optical system according to  claim 1 , wherein when the combined focal length of the meridional cross-section of said eccentric mirror system is defined as fy, and of the eccentric mirrors constituting said eccentric mirror system, the shortest local meridional cross-section focal length is defined as fy min,
   0.5 ≦fy  min/ fy ≦2  
 
     is satisfied. 
   
   
     14. An optical system for directing a beam from display means to a predetermined position, wherein a ray emerging from the center of the display surface of said display means and passing through the center of the exit pupil of said optical system is defined as a central field angle principal ray, said optical system comprising:
 a first optical element having a plurality of eccentric reflecting surfaces, each of the eccentric reflecting surfaces having power and being eccentric relative to the central field angle principal ray, and  
 an eccentric mirror system comprising at least one eccentric mirror having positive power and eccentric relative to the central field angle principal ray,  
 wherein the beam from said display means is condensed and directed to said first optical element by said eccentric mirror system,  
 wherein when in a plane formed by said central field angle principal ray, the angle formed when rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil emerge from said display means and are incident of a first mirror of said eccentric mirror system is defined as θin, and the angle formed when the rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil emerge from the last eccentric mirror of said eccentric mirror system is defined as θout, and the angle formed when the point of intersection is formed on the reflected side when the rays passing from the center of the display surface of said display means to the opposite ends of said exit pupil are extended is defined as positive, and the angle formed when the point of intersection is formed on the opposite side is defined as negative, said eccentric mirror system is designed so as to satisfy 
   0≦θout/θin ≦1.  
 
 
   
   
     15. An optical system according to  claim 14 , wherein the intermediate range is formed larger than the image displayed on the display means. 
   
   
     16. An optical system according to  claim 14 , wherein at least a portion of said intermediate image is formed in the first optical element. 
   
   
     17. An optical system according to  claim 14 , wherein the display surface of said display means is a flat surface, and said intermediate image is curvedly formed. 
   
   
     18. An optical system according to  claim 14 , wherein at least one of said eccentric reflecting surfaces is of a non-rotation-symmetrical shape having only one symmetrical plane. 
   
   
     19. An optical system according to  claim 14 , wherein a beam passing through said first optical element is reflected three or less times. 
   
   
     20. An optical system for directing a beam from display means to a predetermined position, wherein a ray emerging from the center of the display surface of said display means and passing through the center of the exit pupil of said optical system is defined as a central field angle principal ray, said optical system comprising:
 a first optical element having a plurality of eccentric reflecting surfaces, each of the eccentric reflecting surfaces having power and being eccentric relative to the central field angle principal ray, and  
 an eccentric mirror system comprising at least one eccentric mirror having positive power and eccentric relative to the central field angle principal ray,  
 wherein the beam from said display means is condensed and directed to said first optical element by said eccentric mirror system,  
 wherein the central field angle principal ray does not intersect on the optical path in said eccentric mirror system; and  
 wherein when the combined focal length of the meridional cross-section of said eccentric mirror system is defined as fy, and of the eccentric mirrors constituting said eccentric mirror system, the shortest local meridional cross-section focal length is defined as fy min, 
   0.5 ≦fy  min/ fy ≦2.  
 
 
     is satisfied. 
   
   
     21. An optical system for imaging, wherein a ray incident from the entrance pupil of said optical system and passing to the center of the imaging plane is defined as a central field angle principal ray, said optical system comprising:
 a first optical element having a plurality of eccentric reflecting surfaces, each of the eccentric reflecting surfaces having power and being eccentric relative to the central field angle principal ray; and  
 an eccentric mirror system comprising at least one eccentric mirror having positive power and eccentric relative to the central field angle principal ray,  
 wherein a beam from the entrance pupil passes through said first optical element and is condensed and directed to an imaging position;  
 wherein the central field angle principal ray does not intersect on the optical path in said eccentric mirror system; and  
 further comprising at least two surfaces, each of which has power, respectively disposed in an optical path before an intermediate image is formed and between the intermediate image and the exit pupil of said optical system.  
 
   
   
     22. An image pickup apparatus comprising:
 an optical system according to  claim 21 ; and  
 an image pickup means for picking up image information formed by the optical system.